Method of cycling a lithium-sulphur cell

Abstract

A method for cycling a lithium-sulphur cell, said method comprising discharging a lithium-sulphur cell, terminating the discharge when the voltage of the cell reaches a threshold discharge voltage that is in the range of 1.5 to 2.1V, charging the lithium-sulphur cell, and terminating the charge when the voltage of the cell reaches a threshold charge voltage that is in the range of 2.3 to 2.4V, wherein the lithium-sulphur cell is not fully charged at the threshold charge voltage, and wherein the lithium-sulphur cell is not fully discharged at the threshold discharge voltage.

The invention claimed is: 
     
       1. A method for cycling a lithium-sulphur cell, said method comprising:
 i) discharging a lithium-sulphur cell, 
 ii) terminating the discharge when the voltage of the cell reaches a threshold discharge voltage that is in the range of 1.5 to 2.1V, 
 iii) charging the lithium-sulphur cell, and 
 iv) terminating the charge when the voltage of the cell reaches a threshold charge voltage that is in the range of 2.3 to 2.4V, 
 wherein the lithium-sulphur cell is not fully charged at the threshold charge voltage, and 
 wherein the lithium-sulphur cell is not fully discharged at the threshold discharge voltage; and 
 wherein the point at which charge is terminated occurs when at least 80% of the cathodic sulphur is dissolved in the electrolyte. 
 
     
     
       2. The method of  claim 1 , wherein the threshold discharge voltage is about 1.75V. 
     
     
       3. The method of  claim 1 , wherein the threshold charge voltage is about 2.33V. 
     
     
       4. The method of  claim 1 , wherein steps i) to iv) are repeated for at least 2 discharge-charge cycles. 
     
     
       5. The method of  claim 1 , wherein steps i) to iv) are repeated for at least 20 discharge-charge cycles. 
     
     
       6. The method of  claim 1 , wherein the point at which discharge is terminated occurs when at least 80% of the cathodic sulphur material is dissolved in the electrolyte. 
     
     
       7. A battery management system for controlling the discharging and charging of a lithium-sulphur cell, said system comprising:
 a termination device coupled to the coupling device, wherein the termination device terminates the discharge of the lithium-sulphur cell at a threshold discharge voltage that is greater than the voltage of the cell in its fully discharged state, 
 a charging device coupled to the coupling device, wherein the charging device is capable of charging the lithium-sulphur cell, and wherein the charging device is configured to terminate charging of the lithium-sulphur cell at a threshold charging voltage that is lower than the voltage of the cell in its fully charged state, and wherein the charging device is configured to terminate charge when at least 80% of the cathodic sulphur is dissolved in the electrolyte. 
 
     
     
       8. The system of  claim 7 , further comprising a voltage monitor configured to monitor the voltage of the lithium-sulphur cell during discharge and charge. 
     
     
       9. The system of  claim 7 , wherein the charging device terminates the discharge when the voltage of the cell is at 1.7 to 1.8 V. 
     
     
       10. The system of  claim 7 , wherein the charging device terminates the discharge when the voltage of the cell is at about 1.75 V. 
     
     
       11. The system of  claim 7 , wherein the charging device terminates the charge when the voltage of the cell is at 2.3 to 2.4 V. 
     
     
       12. The system of  claim 7 , wherein the charging device terminates the charge when the voltage of the cell is about 2.33V. 
     
     
       13. The system of  claim 7 , further comprising a coupling device configured to receive the lithium-sulfur cell and couple the lithium-sulfur cell to the termination device and the charging device. 
     
     
       14. The system of  claim 7 , further comprising a lithium sulphur battery. 
     
     
       15. The system of  claim 7 , wherein the termination device terminates discharge of the lithium-sulphur cell when at least 80% of the cathodic sulphur material is dissolved in the electrolyte.